This application describes reflecting array antennas or reflectarrays. Previous attempts at developing reflectarrays met with certain difficulties. For example, an X-band 0.75 meter diameter microstrip reflectarray using variable length phase delay lines was developed. This reflectarray demonstrated a relatively high efficiency (70%) with a peak gain of 35 dB for linearly polarized radiation. A 27 GHz microstrip reflectarray using variable-size patches was also attempted. This reflectarray had a diameter of 0.23 meters and achieved a gain of 31 dB with a relatively low efficiency of 31%, again for linearly polarized radiation.
The low efficiency of this latter array may have been in part due to efficiency-susceptibility to fabrication tolerance of patch dimensions at the high millimeter wave frequency. Another reason may be that phase is achieved in this system at the expense of amplitude. Only one correct dimension will resonate at a particular frequency and, by varying the patch sizes, the amplitude of many patch elements are sacrificed.